Use SkPMColor4f in OverrideInput, remove some kruft from SkGr

Bug: skia:
Change-Id: I2263048fea3b708aa0ac7758a80cbdc47e4f45f2
Reviewed-on: https://skia-review.googlesource.com/c/159540
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed